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Many human and physical factors influence the size and distribution of human settlements. These factors include landforms, climate, proximity to bodies of water, natural resources, economic activities, the level of technology, and relationships with neighboring peoples.

Many processes lead to changes in settlement patterns, including urbanization, transportation, access to resources, and economic activities.

Demographers use population density maps, population pyramids, and other geographic data to describe population characteristics and trends. A population density map shows where population is distributed over an area. While a population pyramid shows the distribution of population in a country by age and gender.

The world’s population is now growing at an accelerating rate. Partly due to a longer life expectancy.

Both physical and human factors affect where people settle, even today. Three-quarters of the world’s population now live on less than 5% of Earth’s surface. Most of the world’s population is concentrated in five areas, with more than half in the first two:

Physical factors play a very large role in where people live. Population tends to cluster around seaports and fresh water sources. Much of the Earth’s land surface is unfriendly to human habitation. In fact, eight of the 10 most populous cities in the world are on or near earthquake faults. Population is typically sparse in extremely dry, wet, cold, or mountainous areas. These areas usually have a low population density. People tend to settle in low-lying areas with fertile soil and a temperate or mild climate.

Human factors also affect where people settle. The need to establish a capital city at a central location or to establish new transportation routes that may lead people to settle in a particular area. As technology improves, people are able to explore and settle in new areas, despite physical barriers. Economic activities also bring people to new areas. The discovery of valuable resources, such as gold, diamonds or oil, may attract settlers to an otherwise unfavorable area.

Most anthropologists believe that humans first appeared in the Great Rift Valley in East Africa many hundreds of thousands of years ago. From there, humans spread to the Middle East, Asia, Europe, the Americas and Oceania. Around 10,000 years ago, people in the Middle East discovered they could plant seeds to grow their own food. People no longer needed to follow a nomadic way of life — wandering in constant search of food. Although agriculture was first discovered in the Middle East, it was later discovered independently in China, India, Africa and the Americas.

In some areas, agriculture became especially successful. In the river valleys of Egypt, Mesopotamia, India, and China, which had fertile soil from annual flooding. This led to abundant harvests. People were able to grow a surplus of food to feed a non-farming, urban population. Urban dwellers included new specialized groups — priests, soldiers, traders, scribes, and craftspeople. As urban populations increased in size, a need for government developed.

Starting in the 1700s, the Industrial Revolution greatly increased the speed of urbanization - the movement of greater numbers of people into cities. Towns and cities started to grow around these factories. Cities also grew at points where goods were exchanged or transferred — such as seacoast ports where rivers met, and later, where different railroad lines crossed.

Settlement patterns sometimes change over time. As areas urbanize, surrounding areas attract new settlers. The discovery of new resources or the construction of new transportation routes can also encourage new settlement. The Far West of the United States, for example, was sparsely populated until the discovery of gold in California and the construction of the transcontinental railroad.

In more recent times, suburbs have developed outside cities. Often, these suburbs come to form satellite cities around the older city center. As the population increases further, these cities may merge into a single metropolitan region.

In less developed countries, people often arrive from the countryside without education or resources. These newcomers may settle in squatter settlements or shanty towns, usually found outside of the city. A shanty town is a slum settlement where poor people live in dwellings made from scrap materials — such as plywood, corrugated metal and plastic sheets.

Patterns of settlement and the distribution of the world’s population have changed greatly over time. World population growth was uneven until agriculture was first introduced which then allowed population to grow gradually. Famines, plagues, and wars kept population growth in check. However, during the Industrial Revolution, Europe and North America became the first places to use new farming techniques and to apply modern science to decrease death rates. As a result, population growth accelerated by almost ten times in Great Britain.

As Europeans colonized new areas, they spread their medical advances and new farming methods to these regions. This enabled local peoples to live longer, however, they did not always decrease their birth rates. There has now been a population explosion in Asia, Africa, and Latin America, especially in the years since World War II Many countries in Asia, Africa, and Latin America are now struggling to reduce their birth rates and bring population growth under control. For example, China encourages families in cities and towns to have only one child.

Geographers measure patterns of settlement by looking at population density — how many people live within a given area. They often measure the average number of people in a square mile. Geographers also use special maps to show the distribution of population density.

A dot population map uses dots to indicate where major towns and cities are located. Each dot represents a certain number of residents. The key to the map tells how many people each dot represents. Other symbols, like diamonds or circles, may be used to indicate larger cities.

A population density map can also use patterns or colors to show how many people live in a given area. Regions of different population density are separately indicated. The key explains what each pattern or color represents.

Using population pyramids, demographers study the characteristics of human populations. For example, they compare the numbers of males and females in a society. They also look at the average ages of its members. The pyramid typically shows the number of males on the left side and females on the right. A vertical line runs through the middle with each age group is represented by a different bar. In a sense, a population pyramid is actually a type of bar graph. The different bars are stacked up to create the pyramid.